Liquid fuel pumping apparatus



Dec. 9, 1.969 w. w. NICOLLS LIQUID FUEL PUMPING APPARATUS Filed March13, 1968 WILFRED E.w. NICOLLS //VV/V7ZP PM 4709A")? United States Patent3,482,519 LIQUID FUEL PUMPING APPARATUS Wilfred Edward Walter Nicolls,East Molesey, England, assignor t0 C.A.V. Limited, London, England, aBritish company Filed Mar. 13, 1968, Ser. No. 712,759 Claims priority,applicatlion Great Britain, Mar. 28, 19 67,

67 Int. Cl. F04b 13/132, 49/00; F04d 15/004 U.S. Cl. 103--2 ClaimsABSTRACT OF THE DISCLOSURE This invention relates to liquid fuel pumpingapparatus for supplying liquid fuel to an internal combustion engine andof the kind comprising a bore which defines a pumping chamber, a pumpingpiston slidable in said bore, means for moving the piston inonedirection to reduce the volume of said pumping chamber, and a passageextending from said bore and through which fuel flows from the pumpingchamber to the engine during movement of the piston in said onedirection.

The object of the invention is to provide such an apparatus in a simpleand convenient form.

According to the invention in an apparatus of the kind specified thereis provided a resiliently loaded one way valve having a valve elementwhich is lifted from its seat to permit the flow of fuel from thepumping chamber through said passage and which is further lifted fromits seat by physical contact of the piston therewith.

One example of a liquid fuel pumping apparatus in accordance with theinvention will now be described with reference to the accompanyingdrawing which is a partsectional side elevation of the apparatus.

Referring to the drawing there is provided a body part in which ismounted a rotary cylindrical distributor member 11 which is arranged tobe driven in timed relationship with the engine with which the apparatusis associated. At one end of the distributor member is formed atransverse bore 12 in which is mounted a pair of reciprocable plungers50. Surrounding the distributor member at this point is an annular camring 51 having a plurality of diammetrically disposed and inwardlyextending cam lobes which through the intermediary of rollers 52respectively act to impart inward movement to the plungers as thedistributor member is rotated and the plungers 50 together with the camring constitute a pressure pump.

At the opposite end of the distributor member is mounted the rotary partof a fuel supply pump 13 having an outlet which is in communication witha feed passage 14 formed in the body part. The inlet of the feed pump isconnected in use, to a source of fuel. Within the distributor member isformed a longitudinally extending bore 15 which at one end is incommunication with the transverse bore 12. The other end of thelongitudinal bore is closed by a plug member 16 and a portion of thebore adjacent the plug member is of enlarged diameter.

Extending from this portion of the bore 15 is a radially disposeddelivery passage 17 which is arranged to register in turn and as thedistributor rotates, with a plurality of mice delivery ports 18 formedin the body part. The delivery ports 18 are connected respectively tothe injection nozzles of the associated engine.

Slidably mounted within an intermediate portion of the bore 15 is a freepumping piston 19 which has end portions of reduced diameter.Furthermore, the step which is defined between the wider portion and theintermediate portion of the bore 15 constitutes the seating of a one Wayvalve. The valve element of this valve is defined by a plate 20 which isurged against the seating by means of a coiled compression spring 21.The diameter of the plate 20 is slightly smaller than that of the widerportion of the bore so that fuel can flow past the plate as will bedescribed.

Extending from the bore 15 adjacent the step is an inlet passage 22 anda further inlet passage 23 extends from a further enlarged portion ofthe bore 15 lying between the aforesaid intermediate portion and thetransverse bore 12. The inlet passages 22 and 23 are arranged toregister respectively with inlet ports 24 and 25 which are formed withinthe body part and which communicate at diametrically opposed points witha cylindrical chamber 26 formed in the body part. Moreover, mountedwithin this chamber is an angularly adjustable throttle member 53 whichis provided with a pair of diametrically opposed and longitudinallyextending grooves on its periphery. The inner end of the chamber 26communicates by way of an annular groove formed in the body part, withthe supply passage 14 and the arrangement is such that fuel flowing fromthe feed pump can be proportioned between the ports 24 and 25 byadjustment of the throttle member 53.

During a filling stroke of the apparatus the ports 24 and 25 are incommunication with the passages 22 and 23 respectively whilst thepassage 17 is out of register with an outlet port 18. As fuel flowsthrough the passages 22 and 23 the free piston 19 moves to the left fromthe position in which it is shown in the drawing and at the end of thefilling stroke the bore 15 is completely filled with fuel as also is thebore 12. As the distributor rotates the passages 22 and 23 are moved outof register with the ports, 24 and 25 and the delivery passage 17 ismoved into register with an outlet port 18. During further movement ofthe distributor member the plungers are moved inwardly and fuel underpressure moves the free pumping piston to the right and in so doing fuelis displaced from the pumping chamber defined at the right hand end ofthe piston through the delivery passage 17 and the delivery port 18.During this time the plate 20 is lifted from the seating against theaction of the spring 21. Towards the final movement of the pumpingpiston the reduced end thereof contacts the plate 20 and lifts itfurther from its seating.

The free pumping piston continues to be moved by the action of fuelunder pressure expelled from the transverse bore 12 until spill passages30 which extend from the bore 15, are exposed by the left hand end ofthe piston. As soon as this occurs the pressure at the left hand end ofthe pumping piston is relieved and any surplus fuel escapes through thespill ports 30 which during this time are in communication with spillports 31 formed in the body part.

The delivery of fuel to the engine ceases as soon as the piston isbrought to rest and when the excess fuel has been discharged the pistonis moved in the reverse direction by the action of the spring 21. Duringthis movement a quantity of fuel flows from the pipe line whichinterconnects the outlet port 18 with the nozzle, into the bore 15.After a predetermined quantity of fuel -has returned the plate 20 willbe urged back onto its seat. When this occurs no further fuel can flowfrom the pipe line. It will thus be seen that the quantity of fuel whichis returned from the pipe line to the bore 15 depends upon the movementof the piston during the movement of the plate onto its'seat. 4

If the piston is of sufficient mass its inertia will cause it tocontinue its movement to deliver fuel to an outlet after the spill port30 has been opened. The inertia depends upon the speed at which thepiston moves and since this is dependent upon the speed at which theapparatus is driven the degree of unloading of fuel from the pipe linecan be made to vary in accordance with the speed at which the apparatusis driven.

If desired a pressurising valve 54 may be provided in the spill passage31. The effect of this valve is to assist the inertia of the pumpingpiston 19 since it will ensure that pressure is always applied to theleft hand end of the piston even though this pressure may beconsiderably lower than the pressure which is attained during theinjection stroke. The characteristic of the pressurising valve may beadjusted to provide any required degree of unloading.

As the distributor member is rotated from the position in which it isshown in the drawing the delivery passage 17 is moved out of registerwith the delivery port 18 and the inlet passages 22 and 23 are broughtinto register with the inlet ports 24 and 25 respectively to fill thebore 15 with fuel for the next injection stroke.

Having thus described my invention what I claim as new and desire tosecure by Letters Patent is:

1. A liquid fuel pumping apparatus for supplying fuel to an internalcombustion engine and comprising in combination, a pressure pumparranged to be driven in timed relationship with an engine with whichthe apparatus is associated, a bore, and to one end of which fuel isdelivered by the pressure pump during a pumping stroke thereof, apumping piston slidable in said bore and movable towards the other endof said bore during a pumping stroke of the pressure pump, a passageextending from said other end of the bore and through which fuel flowsto the engine during movement of the piston towards said other end ofthe bore, a seat defined about said bore adjacent the other end thereof,a spring loaded valve element which is lifted from the seat to permitthe flow of fuel from the other end of the bore through said passage andwhich is further lifted from the seat by physical con tact of the pistontherewith, the piston under the action of the spring loading of thevalve element moving towards said one end of the bore at the end of thepumping stroke of fuel to flow into said otherend of the borethroughsaid passage before the valve element contacts the seat.

2. An apparatus as claimed in claim 1 including a port formed in thewall of said bore, said port being uncovered to a drainby the end of thepiston adjacent said one end of the bore when the piston attains apredetermined position after contacting said valve element and .duringits movement towards the other end of the bore, the final position atwhich the piston stops being determined by the inertia thereof.

3. An apparatus as claimed in claim 2 including a pressurizing valveoperable to limit the extentof the reduction in pressure of fuel actingon the end of the piston adjacent said one end of the borewhen said portis uncovered.

4. An apparatus as claimed in claim 3 including a rotary cylindricaldistributor member mounted in a body part and arranged to be driven intimed relationship with the engine with which the apparatus isassociated, said passage breaking out onto the periphery of thedistributor member, and being arranged to register-in turn as thedistributor member rotates, with a pluralityof outlet ports formed inthe body' part-and which in use, are connected respectively to the'injection nozzles of the associated en gine,'the action ofthe' pistonand valve element when moving in the other direction being to allow areturnflowv of fuel through said passage before the valve closes, the

volume of such return flow being substantially constant for each outletport.

References Cited UNITED STATES PATENTS Q g Harris 103-41 X DONLEY J.STOCKING, Primary Examiner W. J. KRAUSS, Assistant Examiner US. Cl. X.R.

